Mail storage structure and rules

Hello,

I am trying to understand how emails and attachments are stored on my Mac. I know they reside in Librairy/Mail/ but what I would like to understand is how attachments are separated from their emails. I see a few cases:

The email does not have an attachment and is stored as emlx
The email has attachment and is stored as in a partial.emlx format. Two possibilities for the attachments:
- They are stored as emlxpart in the same folder as the email
- They are stored in ../Attachments/EmailNumber/ under their own number and in their own format (.pdf, .doc etc. but not in emlxpart format)

Questions:

Are there other possibilities? I saw for instance a movie of 50Mb which was not stored under an attachment number bur direction under ../Attachments/ and within the email this attachment was refered as an "Remote-Attachment-URL" with a link to icloud.
Are there rules regarding whether an attachment is saved in the same folder as the email in a emlxpart format? What triggers an attachment to be stored in its native format vs in emlxpart?
Is there a reason some attachments have floating numbers (ex. 1.2, 2.4) when others have integers?

Thank you for your help.

Best regards,

Thomas

Posted on Sep 25, 2023 10:27 PM

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16 replies

MrHoffman

Level 10

162,443 points

Oct 12, 2023 8:18 AM in response to TCambazard

TCambazard wrote:

No dev budget, I'll work on it until it works (which is almost the case, see my previous post detailing my findings). I have a Mac as mentionned. Is there a way to import the User/Lib content in the iOS's Mail application? I haven't found options to do so so far

You keep writing about iOS mail.

If you have a Mac, you can or do have macOS on that. Definitely not iOS. iOS does not run on Mac.

If you do have a Mac, restore the macOS backup on that, and export the data from macOS into mbox format.

Import or export mailboxes in Mail on Mac - Apple Support

Or copy the mail back up to the mail server from the now-restored macOS environment, and migrate to another platform from there.

There are likely third-party tools to migrate to or from Outlook PST files, as well. Those too run from macOS itself, and not from some other platform extracting data an image.

The likelihood of finding an existing tool available within your lack-of-budget that extracts data from an arbitrary mail store version from an arbitrary image of an arbitrary macOS version (macOS, not iOS) of an arbitrary macOS login is… exceedingly low. Possible, sure, but the audience for such a tool isn’t much past yourself and those people using or working on forensics tooling, and forensics tooling usually has indirect and quite commonly direct costs involved.

And to be absolutely clear, iOS does not and cannot import directly from a macOS disk image, and you’ll need to create that tooling yourself if you want that.

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Mail storage structure and rules